Apparatus for lapping shoulders



May 20, 1952 R. G. RosHoNG 2,597,382

APPING SHOULDERS Patented May 20, 1952 lUNITED S'TATES PATENT OFFICE w 2,597,382 APPARATUS 'FOR LAPPING SHOULDERS Raymond G. Roshong, North Hollywood, Calif., assig-nor lto Grane Packng Company, Chicago, Ill., a corporation ofIllinois Application November 1, 1949, Serial No. 124,788

'3 Claims.

This invention relates to an apparatus for grinding or lapping surfaces and particularly 'to an apparatus for lapping a surface on an object which is axially spaced from either end thereof so that the surface defines a. shoulder on the object. Such articles may be valve plates, rotary seal seats, etc. for hydraulic equipment or the like. For purposes of illustration, this invention will be described with reference to its application to valve plates.

It is desirable in many instances to design a valve disc in such a way that smooth fiow of the fiuid controlled by the valve may be effected past the valve while said valve is partially open. This is accomplished by providing a rounded extension on the valve disc which projects into the stream to help guide the flow of the liquid. The seat for the disc, however, is located between the ends of the valve disc so that the sealing surface on the valve disc adapted to contact the seat is axially spaced from the extension. To prevent leakage of fluid past the seat, the seat and disc mating surfaces must be lapped to a perfectly flat contour. Such lapping, however, is difiicult to achieve inasmuch as no conventional fiat lap can be used on the entii'e mating face on the valve disc due to the presence of the extension.

It has been customary in the past to perform the lapping operation on valve discs by using a fiat lap having an opening therein to receive the protruding end of the disc, the valve disc being rotated on the lap about the axis of the opening.

This, however, does not permit the continuous `presentation of a different lap surface to the disc during the lapping operation and hence the grooving of the lap and the consequent nonuniform lapping of the disc.

Another'object of this invention is to provide a lap for lapping valve discs or .the like of the type above described, wherein those areas of the lap not operated upon by the valve disc are continuously abraded at substantially the same rate as the portion in contact with the valve disc, thereby maintaining the lap in its original condition throughout an indefinite number of cycles. A feature of this invention is the provision of means for holding one or more valve discs or the like on the lap while a shoulder or the like on each valve disc is being lapped.

These and other objects and features of this invention will become apparent from the following detailed description when ytaken together 'with the accompanying drawings, in which Fig. 1 is a fragmentary plan view of la lap on which is placed a valve disc with a sealing vsurface to be lapped, the surface being located axially 'inwardly from the end of the disc; and

Fig. 2 is a fragmentary elevation in section taken along the line 2-2 of Fig. 1.

Referring now to the drawings, there is sh'own in Fig. 2 a valve disc having a fiange or shoulder intermediate the ends thereof, said shoulder extending radially out-wardly and terminating in an annular bead |2. A radially disposed surface |3 on bead |2 constitutes the sealing surface of the valve disc. Said surface is designed to cooperate with aA mating radially disposed surface (not shown) in a Valve body to provide a fluid-tight Seal therebetween and hence must be perfectly flat and smooth. Extending axially beyond surface I3 is a rounded portion 14 on the valve disc which normally protrudes into the fluid .stream passing through the valve and assists in promoting a smooth flow of the stream through the valve to minimize cavitation and other detrimental effects. The opposite end' 15 of the valve has a recess IG which may be round and machined for attachment to the valve stem. The exact construction of the various elements of the valve disc are nt material to this invention other than that surface l3 is spaced axially from ends |4 and 15.

The lap by which the valve disc l0 is lapped in accordance with this invention is comprised of a circular plate l 'I (Figs. 1 and 2) having a raised annular region IB near the center thereof and another raised annular region IS adjacent the perimeter thereof, the surfaces 20 and 2| of which lie in a common plane and are perfectly fiat and smooth except for radially disposed grooves 29 which serve to carry away excess grit and the cuttings. The space 22 between the raised regions |8 and |9 constitutes a continuous groove into which extension Ill of the valve disc |0 protrudes. The bottom of the groove, however, does not contact extension |4 at any time. Valve disc 10 is supported on surfaces 20 and 2| of raised Sections |8 and |9 by bead |2, surface |3 thereof resting directly on surfaces 20 and 2| and bridging groove 22. shown) are provided to rotate lap about its center during the lapping cycle.

Thus, it isobvious that the valve disc l0 will be operated upon by the lap l'l solely at surface I3, and when disc |0 is suitably rotated so that the portions of surface |3 bridging groove 20 may be turned to contact raised regions |8 and |9, all parts of the valve disc surface |3 will be operated upon by the lap Il.

The plane of raised regions |8 and |9 is maintained fiat by means of one or more rings 23 Suitable means (not I which encircles valve disc 10 and rests upon the said regions. The ring 23 serves to wear the raised regions 18 and |9 at a higher rate than does surface |3 of disc so that said regions 18 and |9 are maintained in their initial condition indefinitely. It should be noted that ring 23 has a surface 24 which operates upon those portions of raised regions |8 and IB not contacted by surface |3 and hence any tendency to groove the lap |1 by surface |3 is immediately eliminated. To insure this desirable effect, a weight 25 is placed on ring 23 so that the unit pressure exerted by ring 23 and weight 25 is greater than the unit pressure produced by valve disc |0. Said weight 25 is recessed at 26 so as to provide a shoulder for centering it with respect to ring 23, and both the weight and ring are thus constrained to move together in a lateral direction.

- It'is contemplated that more than one valve disc l|0wi1l be lapped at a time and accordingly as many such discs |0 and rings 23 may be placed on the lap |1 as space will permit.

Weight 25 is restrained against movement with lap |1 by means of a pin 21 which may be held in a fixed part of the machine frame shown schematically at 28. Said pin 21 may be raised or lowered relative to the frame 28 to enable the operator to remove weight 25 from ring 23, thereby gaining` access to valve disc to remove said disc from the lap or to insert one to :be lapped.

The rotation of lap l1 about its axis causes different portions of the lap surface to be presented to surface |3 on disc 10 in accordance with good lapping practice. This rotation also induces a rotation in the ring 23 and weight 25 about pin 21. Valve disc 10 must also be rotated and this action is effected by means of a guide plate 30 which is secured by a nut 3| to the lower end of pin 21. Said plate 30 holds the disc 10 against movement wtih the lap |1 and also holds the disc |0 away from ring 23, thereby preventing a tilting of the disc |0. For greater freedom of rotation, plate 30 may |be mounted loosely to avoid any interference with the rotation of disc |0. For valve discs which are not very high, plate 30 may be dispensed with and the disc will then be in contact with ring |3 during the lapping operation.

`,."Thus there is produced a rotation of disc I 0 about its axis simultaneously with the rotation of lap |1 together with the rotation of ring 23 about pin 21, all of which insures a continuous wearing of lap |1 at raised regions |8 and l9 which in turn results in, first of all, a lapping of surface |3 to the desired flatness and, secondly, a continuous conditioning of raised regions 18 and I 9 by ring 23.

It is apparent from the foregoing that there has been provided a means for automatically lapping Shoulders or the like on valve discs or similar objects, which is automatic and results in the least localized wear on the lap. Furthermore, the lapping operation is automatic and it prevents, as faras can be reasonably determined, the formation 'ofa definite wear pattern on the lap which would be detrimental to the quality of the finished surface on the said discs or shouldered objects.

It is understood that the foregoing description is illustrative of preferred embodiments of this invention and that the scope of the invention is not to be limited thereto, but is to be determined by the appended olaims.

What is claimed is:

1. Apparatus for lapping a surface on a shoulder of a valve disc or the like, said apparatus comprising a circular lap having at least one groove formed in the operative surface thereof, said groove being concentrically disposed with respect to the lap and of sufficient width and depth to receive the portion of the valve disc extending beyond the shoulder, a ring encircling the valve disc and resting upon the operative surface of the lap, a weight on the ring, said weight being recessed to receive the ring and said weight having a centrally disposed opening, a pin loosely fitted into the opening to Dermit rotation of the weight about the pin, and means for holding the pin against movement with the lap.

2. Apparatus for finishing a surface on a, shoulder or the like of an article, said article having a central opening therein, said apparatus comprising a rotatable lap having an annular groove to receive an article with the portion thereof extending beyond the shoulder disposed in the groove, guide means extending into the central opening in the article, a conditioning ring resting on the lap and encircling the article, a weight on the ring, locating means between the weight and ring to fix the position of the ring relative to the weight, means on the weight for fixing the position of the guide means relative to the weight, and means also on the weight for holding the ring against revolution with the lap.

3. Apparatus for finishing a surface on a shoulder or the like of an article, said article having a central opening therein, said apparatus comprising a rotatable finishing lap having an annular groove to receive an article with the portion of said article extending beyond the shoulder disposed in the groove, a frame member extending over the lap, a pin in the frame member, a plate rotatably mounted on said pin and extending into the central opening in the article to hold the article against revolution with the lap, a conditioning ring on the lap and means for rotatably mounting the ring on the said' pin,

said means for rotatably mounting the ring onthe said pin comprising a'weight extending over the ring and having a shoulder for centering said weight on the ring and a central opening through which the said pin passes.

RAYMOND G. ROSHONG.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PA'I'ENTS 

